In order to analyze an integrated circuit formed on a semiconductor substrate, it is necessary to perform optical analyses of the circuit in operation, for example by light-emission microscopy or using a scanning electron microscope.
Nevertheless, it is difficult on a real circuit to locate the exact point of the circuit where a measurement is to be performed. This task is made even more difficult in numerous cases, for example with programmable circuits, because the exact configuration of the real circuit is not known. Thus, the real coordinates of the tracks of the circuit are not available. In addition, the tracks of the circuit are often smaller in size than the positioning error of the tool used for observing the circuit.
In contrast, the circuit diagram of the circuit is generally available, even if the real layout of the circuit on the semiconductor substrate is not available.